Spin forming techniques are used to manufacture tanks, drums and other vessels. For example, spin forming techniques are used to manufacture vessels ranging in size from fire extinguishers to heads for concrete truck drums. Spin forming techniques commonly include rotating a cylindrical tube about its longitudinal axis, while concurrently heating an end portion of the tube. The tube is formed by applying pressure to the heated end portion to either constrict or expand the end portion of the tube. In this regard, U.S. Pat. No. 2,408,596 (Bednar et al.) discloses a method for forming cylindrical ends by torch heating, rotating, and applying pressure to a cylindrical work piece. Pressure is applied by a tool moving in arcuate paths that curve toward a desired contour of the work piece. Similarly, U.S. Pat. No. 5,235,837 (Werner) discloses an apparatus for producing thin-walled cylindrical pressure vessels or tanks through metal spinning operations. A cylindrical work tube is rotated about its longitudinal axis, and the end of the work tube is heated by heating torches. Forming rollers are moved along a plurality of arcuate stroking paths to shape the end of the work tube. The arcuate stroking paths curve toward a desired final shape of the work tube.
U.S. Pat. No. 5,598,729 (Hoffmann et al.) discloses another method for spin forming a metallic tube. The metallic tube is rotated about its longitudinal axis, and inductive heating elements are used to heat an end portion of the tube. Forming rollers are used to form the heated end portion of the tube. The forming rollers are moved along a succession of angularly spaced apart, substantially straight forming passes.